Some window glass for vehicles particularly for automobiles has an infrared reflection film to prevent an increase in the car interior temperature. Heretofore, to obtain a high infrared reflection performance, an electrically conductive thin film represented by a silver type metal thin film has been used for the infrared reflection film. However, if the electrically conductive thin film is laminated on a glass plate, a radio wave transmission performance remarkably decreases. Further, in such a case, the decrease in the radio wave transmission performance is a decrease over a wide range of from the near infrared region to the radio wave region. The decrease in the radio wave transmission performance leads to malfunction of an infrared sensor such as an optical beacon or a rain sensor or decrease in receiving performance of a television, a radio or the like. Therefore, a window glass having a high infrared reflection performance has hardly been mounted on a vehicle having such a function.
Therefore, as a window glass shielding infrared rays while securing the radio wave transmission performance, a laminated glass employing an interlayer made of a polyvinyl butyral (PVB) or the like having infrared shielding fine particles dispersed therein (hereinafter referred to as a “fine particles-dispersed interlayer”) (e.g. Patent Document 1, hereinafter a laminated glass of this type will be referred to as a “fine particles-containing laminated glass”) has been employed. With respect to the fine particles-containing laminated glass, for example, by use of tin-doped indium oxide (hereinafter referred to as “ITO”) fine particles as the infrared shielding fine particles, an infrared shielding performance can be imparted to the interlayer by the ITO fine particles, and in addition, since the ITO fine particles are dispersed, the decrease in the sheet resistance of the interlayer can be prevented. Accordingly, the fine particles-containing laminated glass is useful as a window glass shielding infrared rays while securing the radio wave transmission performance.
However, the fine particles-containing laminated glass is considered to have the following disadvantages as a window glass which is required to have a higher infrared shielding performance. One is a not so high shielding properties against light in the infrared region, e.g. at a wavelength in the vicinity of 1,000 nm (e.g. prior art in Patent Document 2). The other is the fine particles-dispersed interlayer absorbing infrared rays, thus leading to reradiation of the absorbed solar energy to the car interior (e.g. prior art in Patent Document 3).
Patent Document 1: JP-A-2001-151539
Patent Document 2: JP-A-2005-89244
Patent Document 3: JP-A-2004-26547